Charlie Crist's decision in 2009 to not seek a second term as governor and to make an ill-fated bid for a U.S. Senate seat had a dramatic effect on the direction of Florida politics.

It opened the door for "Rick who?" to run for governor.

It allowed Jeff Atwater and Pam Bondi to win statewide office.

It changed career paths for Bill McCollum and Alex Sink, trickling down to affect other Republicans.

It was a game-changer.

Crist is the only governor in Florida history not to seek re-election since the two-term limit was created in 1968.

He renounced his Republican ties in 2010, ran as an independent Senate candidate, lost to Republican Marco Rubio and is now trying to reclaim his former job as a Democrat.

That makes him the first to mount a credible candidacy for governor as both a Republican and a Democrat.

In pondering what might have been, speculation is unavoidable.

If Crist had run for re-election as a Republican, he would have been a heavy favorite to win, even after hugging President Barack Obama in a state where the unemployment rate soared above 11 percent.

In a statewide poll by Quinnipiac University in April 2010, a few weeks before Crist left the Republican Party, 49 percent of voters approved of his job performance and 39 percent disapproved — better numbers than Gov. Rick Scott has received in any Quinnipiac poll.

Consider, too, that Scott would not have taken the risk of challenging an incumbent governor of his party.

McCollum probably still would be state attorney general and Sink likely would be chief financial officer. Swept up in the tide of Crist's ambitions, both left their Cabinet posts after a single term to seek the open governorship, and both lost to Scott.

"I would have run for re-election. I enjoyed being attorney general," said McCollum, who now works for a law firm in Washington, where he served 20 years in Congress. "I had no intention of running for governor until Charlie made that stunning announcement."

Had Crist been re-elected, he would have had to deal with the messy aftermath of the June 2010 indictment of Jim Greer, the former state Republican Party chairman now in prison after pleading guilty to stealing party money.

He would have been forced by circumstances to campaign for Mitt Romney, the 2012 Republican presidential nominee, who needed a Florida victory to beat Obama and didn't get it.

Crist presumably still would be a moderate Republican and be the object of much wrath from the tea party. He would have had to endure the rest of the economic collapse and the recovery Scott is now celebrating.

He likely would have cut a ribbon to herald the start of high-speed rail between Tampa and Orlando.

And, this being Crist, he would be thinking of his next campaign and higher office. The highest office, to be exact.

By now, Crist would be approaching the end of his second term as a centrist Republican governor of the nation's largest swing state and likely would be in the conversation of potential GOP presidential contenders in 2016 — which many think was what Crist wanted in the first place.

"Charlie right now would be out there running for president as a nicer Chris Christie," said lobbyist and Republican fundraiser Brian Ballard, referring to the centrist New Jersey governor with a reputation for volatile behavior. "He would be in the catbird seat and he'd be one of a handful of people being talked about right now."

Perhaps. But it also might have been a challenge for Crist to find room in a field of potential Republican presidential candidates that includes former Florida Gov. Jeb Bush and Sen. Rubio.

It's conceivable that as the economy recovered and the unemployment rate continued to fall, Crist's popularity would have remained steady.

With Crist on his way out of office at the end of a second term, the 2014 field would be open. Consider that the leading candidate likely would be Adam Putnam, who was elected agriculture commissioner in 2010 because his predecessor, Charlie Bronson, was term-limited.

Putnam, a student of Florida politics, said the biggest domino fell in August 2009, when Republican U.S. Sen. Mel Martinez quit in the middle of his term. Crist appointed his former chief of staff, George LeMieux, to the seat that ultimately would be won by Rubio.

"It's a game-changer for the trajectory of so many careers," Putnam said.

Darryl Paulson, professor emeritus of government at the University of South Florida St. Petersburg and a Republican who has followed Florida politics for decades, speculated that if Crist had stayed on as governor, he could have helped guide the GOP closer to the political center.

"Gov. Crist did have some very positive moderating effects on the Republican Party," said Paulson, citing Crist's record on race relations and expanding early voting in the 2008 election.

Paulson said that with Crist in office and not Scott, it's highly unlikely that the state would have launched a pair of controversial efforts to purge the voting rolls of noncitizens, leading to lawsuits and widespread allegations of voter suppression tactics.

Crist's style had worn very thin with many Republicans by the spring of 2010, which hastened his exit from the GOP.

So another unknown is the intensity of dislike for Crist by the conservative base of the Republican Party, how he would have handled it, and how badly his relationships would have worsened with Republicans in the Legislature. Crist despised the tea party crowd when he was a Republican, and the feeling was mutual.

The full impact of Crist's game-changing move won't be realized until November.

Crist faces a Democratic primary opponent, former state Sen. Nan Rich, whom he refuses to debate, but with massive advantages in money and name recognition, he is widely expected to be the Democratic nominee.

As evidence, the Republican Party of Florida is devoting substantial effort to daily criticism of Crist's record.

Crist, the former Republican whose Capitol Hill ambitions created a once-in-a-life political opportunity for Scott, now wants to be the Democratic savior who drives Scott out of office.

Asked what might have been had he stayed put, Crist refused to look back.

"I'm looking forward," Crist said. "To the next four years."

Steve Bousquet can be reached at bousquet@tampabay.com or (850) 224-7263.